1. Field of the Invention
The invention relates to a silo for bulk material, with a centrally arranged mixing and homogenizing chamber to which the bulk material is fed by ventilation of the silo base.
2. Description of the Prior Art
In known mixing silos, as seen, for example, in German Pat. Nos. 15 07 888, of Nov. 20, 1970, and in silos with a central homogenizing chamber, as seen, for example, in German patent applications Nos. P 26 57 596.2, filed Dec. 18, 1976, and P 26 57 597.3, filed Dec. 18, 1976, and in U.S. Pat. application Ser. No. 790,961, filed Apr. 26, 1977, the falling in or funneling in of bulk material into so-called mixing funnels takes place within the main silo space by the action produced by the ventilated silo base. In the centrally arranged chamber, this pre-mixing is followed by an intensive mixing or homogenization of the material. The feeding of the pre-mixed bulk material into the central chamber takes place from the floor of the base of the main silo through apertures on the periphery of the chamber. By suitable ventilation control, and in dependency on the loosening pressure value of the bulk weight of the material and the prevailing flow performance or behavior of the bulk material between the main silo space and the central chamber, a so-called communicating effect is achieved which results in a specific filling level within the chamber.
As proved by experiences with a multiplicity of such mixing silos now in operation, very good operating results can be achieved by such a mixing apparatus. The compact structure, the low power requirements, and the elimination of otherwise customary intermediate transportations contribute further to the economic usefulness of such a device.
In order to obtain optimum operational results with respect to the mixing quality, however, it is necessary to carry out, prior to the construction of such a silo, as accurate as possible an adjustment between silo dimensioning, material passage, bulk weight, fineness of the bulk material, and the air containing capacity and flow performance thereof, especially of the powdered component, with the required pneumatic loosening systems. Once the silo and especially the chamber dimensions have been determined and the silo has been built according to these data, a subsequent correction of the flow-in levels for the chamber is only possible by means of control or selection of air distribution and pressure difference. This may be sufficient in some applications, but there are instances wherein such a belated correction by the aforementioned means is either impossible or incomplete. Further, there are cases wherein on account of the limitation of the capital investment required for the silo, or of changes in material passage or bulk conduct which may show up later, conditions occur that no longer permit an optimization of the mixing quality by means of ventilation control.